Zombies is the name for animated corpses. Zombies are dead humans or undead monsters who are brought back to life through means of vodoun or Voodoo and witchcraft like a priestess of voodoo magic in ancient times sometimes a witch doctor during the ritual in order to do their bidding like in the old movie in black and white, Night of the Living Dead. They are trapped in the same body forever.
Ghoulia Yelps and her sister Moanica Yelps are the zombies in Monster High. Other zombies in Monster High are Ghoulia Yelps's boyfriend, Sloman "Slo Mo" Mortavitch and Neighthan Rot, on his father's side.
In the new Monster High reboot we are introduced to new group of zombies led by Moanica D'Kay. Other zombies are the same but she has some special abilities, like she can speak to other monsters and she can walk normally, something that other zombies aren't able to.